The present invention relates to a diaphragm fluid pump, and more particularly to an improvement of a diaphragm piston assembly of a fluid pump of the type wherein lubrication oil is applied to the driving mechanisms of the diaphragm piston assembly.
In the conventional fluid pump of this type, a sealing member is installed between a portion of an operation rod of the piston assembly and the inner wall of a pump housing so that the flexible diaphragm made of a resilient material, such as rubber and the like, is protected from permeation of the lubrication oil to cause hardening and breakage of the diaphragm. The sealing means of the conventional type has, however, a drawback that the sealing feature of the sealing means becomes less in a short period of time since the sealing area against the operation rod is small.